1. Field of the Invention
The invention pertains to a cyclical thermal management system for maintaining a high altitude platform within a particular altitude range. More particularly, the invention pertains to a long duration, energy efficient, cyclical thermal management system for maintaining high altitude vehicles at a particular altitude and pitch attitude by cyclically manipulating the temperature of one or more of the lifting gases or ballast components in the high altitude platform in response to the effects of diurnal heating and nocturnal cooling cycles and seasonal variations in daylight cycles, the solar flux, and the albedo flux from earth.
The novel cyclical system of the invention responds to the sun's cyclical heating and nocturnal cooling of lifting gases in geostationary high altitude platforms by a corresponding cyclical regulation or manipulation of the temperature of the lifting gas or ballast components and hence buoyancy of the platform to maintain the platform within a particular altitude range and at a particular pitch attitude. The cyclical thermal regulation or manipulation of the lifting gas or ballast components involves not only a daily cycle responsive to the heating and cooling of the lifting gas by the sun, but also the seasonal cyclical pattern of the climate of the particular geostationary location above the surface of the earth.
The cyclical regulation or manipulation of the lifting gas is achieved by processing energy by utilizing cyclical heating and cooling physical actions and chemical reactions alone or together with the chemical or mechanical processing of a portion of the lifting gas or ballast components to maintain a particular altitude or altitude range as well as the potential for future replenishment and storage of lifting gas in a non buoyant ballast compound. The cyclical processing of heat alone or together with the processing of the lifting gas or ballast components is the basic part of the novel active system of the invention.
Buoyancy control in accordance with the best mode of the invention is achieved by a combination of active and passive systems wherein the passive system is designed to reduce the volume of material processed or energy transfer manipulations required from the active system. The combination of a cyclical active system with the passive system also reduces energy and power requirements for maintaining a geostatic position. The related prior art has used the term "geostationary" to describe a predetermined horizontal position but not maintaining a predetermined altitude and pitch attitude. As used herein the term "geostatic" will be used to refer not only to a predetermined horizontal position but also a predetermined altitude and pitch attitude of the novel high altitude platform.
The cyclical active system involves a diurnal as well as a seasonal manipulation of the lifting gases or ballast components by either the conversion of a portion of the lifting gas into a material of less buoyancy as ballast and then later reconverting all or a portion of the material of less buoyancy back into a lifting gas or by an increase in the weight of the ballast component and then later decreasing the weight of the ballast component. For example, hydrogen and oxygen can be processed on a daily basis to provide physical and chemical exothermic reactions during the night to heat the lifting gas at night and provide water. Water produced at night is stored in a water ballonet where in freezing it stores energy in the form of latent and sensible heat which is used to help cool the lifting gas in the early morning before the water is reprocessed during the day to store the sun's energy for use in generating heat during the next night to control buoyancy. For seasonal variation water can be disassociated into hydrogen which is used as additional lifting gas during the winter and oxygen can be expelled into the stratosphere. In the summer oxygen can be reacquired from the stratosphere and recombined with the hydrogen lifting gas to produce water to reduce the volume of the lifting gases, increase the weight of the ballast components and increase the volume of recyclable energy storage materials available for heating and cooling processes to heat and cool the lifting gas.
The cyclical active system also involves a diurnal and seasonal manipulation of the temperature of the lifting gas utilizing heating and cooling physical processes and chemical reactions of the lifting gas or ballast component. The cyclical active system also includes a system for replenishing lifting gas lost through diffusion or the cyclical conversion and reconversion process or as may be required by seasonal variations for a particular geostatic location.
The cyclical active system also provides for the mechanical manipulation and regulation of the lift properties of the lifting gas by utilizing lifting gas circulation fans, shutters or louvers for shielding the lifting gas and variable heat conductance systems. The cyclical active system preferably also includes separately inflatable and deflatable layers for selectively varying the heat transmitted through the skin in relation to its relative position to the sun. These active systems are combined with various passive systems such as utilizing materials having desirable convective and radiative properties for various components including the utilization of heat and radiation reflective layers, a white coating on upper surfaces, no coating on the lower surfaces and materials having desirable convective and radiative properties for various components to reduce the volume of materials or the number of heat transfer manipulations required from the active system to maintain a geostatic position.
2. Description of Related Prior Art Including Information Disclosed Under 37 C.F.R. 1.97 and 37 C.F.R. 1.98
Typically high altitude platforms are specialized types of balloons, dirigibles and lightweight platforms that are maintained aloft with a buoyant gas. These specialized prior art stratospheric platforms have remained aloft only for short durations which is typically a few days and at best a few weeks. For purposes of greater utility such platforms need to be maintained at a predetermined position which requires engines or other propulsion systems to maintain the high altitude platform over a predetermined location on the earth as stratospheric winds are encountered.
Prior art platforms referred to as geostationary were not geostatic due to the extreme temperature variations between the day and night at high altitude which caused the heating and expansion of the lifting gas during the day resulting in altitude gain, increased skin pressure and increased rates of diffusion of the lifting gas through the skin as well as possible failure of the skin material. The problem of increasing altitude during the day if not corrected in the prior art by venting or engine power is cumulative since each increase in altitude results in further expansion of the lifting gas and further lift and further skin pressure due to the decreasing density of the ambient air at higher altitudes. At night the nocturnal cooling of the lifting gas results in decreased volume and pressure and decreased altitude which could cause the platform to crash to the earth.
The conventional prior art solutions to the diurnal heating and nocturnal cooling cycles included venting a portion of the lifting gas during the day to reduce lift in an effort to maintain altitude and the integrity of the skin and a dropping of ballast at night to maintain altitude. This process of venting and dropping of ballast was for a flight duration limited by the volume of lifting gas and ballast. Another conventional prior art solution is the utilization of superpressurization to maintain altitude. The superpressurization solution required a balloon to maintain a constant volume with high internal pressures of 15,000 to 20,000 p.s.i. which put additional stress on the skin material and components that hold the skin together as discussed in Rand, et al. U.S. Pat. No. 5,104,059.
The conventional prior art also could rely upon engines, elevators and wings to divert power to maintain a geostationary position as well as a particular altitude but at the expense of pitch attitude and large amounts of energy. The sacrifice of pitch attitude sacrifices utility due to the resulting inability to control the footprint or field of vision from the platform. The additional problem of sacrificing energy results in a sacrifice of flight duration. The problem with these prior art solutions is the geostatic position of the platform is limited by the amount of energy the platform can carry, store or obtain from the outside environment which is typically sunlight. The more power required to maintain position, altitude and pitch the shorter the flight duration.
The invention unlike the prior art maintains a geostatic position by cyclically processing temperature, lifting gases and ballast weight in response to the diurnal cycles and seasonal variations and when necessary replaces lifting gases lost through diffusion or conversion by varying the chemical composition of the lifting gas and/or ballast. The invention provides for the thermal treatment of the lifting gas utilizing solar energy to maintain a geostatic position and to control skin pressure and lifting gas density during the daily heating and nocturnal cooling cycles as well as seasonal variations to provide a long duration high altitude platform. The invention provides for not only an active system for cyclically manipulating the temperature of lifting gas and the chemical nature of the lifting gas or ballast utilizing solar energy but also provides for a passive system which cooperates with the active system to minimize the magnitude of the manipulations of the active system to maintain a geostatic position.
The related art is best described as geostationary high altitude long duration lighter-than-air platforms. High altitude refers to platforms capable of maintaining an altitude of 50,000 to 120,000 feet for prolonged periods of time and that are capable of maintaining a geostationary position with respect to a predetermined geographic area. Due to the different ambient temperature, pressure and atmospheric conditions in the stratosphere as opposed to the troposphere much of the prior art pertaining to dirigibles and balloons operating in the troposphere is not applicable to geostationary high altitude long duration lighter-than-air platforms.
The related high altitude long duration prior art recognizes the importance of staying aloft for prolonged periods of time in a predetermined geographic position. The geographic position is generally defined in terms of a horizontal position over a predetermined location and not in terms of a cyclical thermal management system for maintaining both horizontal position over a predetermined location and altitude as well as the pitch attitude and pitch angle of the high altitude platform. Wurst, et al. U.S. Pat. No. 5,518,205 provides a high altitude lighter-than-air vehicle that maneuvers during daylight hours to capture as much solar energy as possible during the day to operate the propellers, avionics and a gondola shifting mechanism. Excess energy is stored as electricity in batteries with the preferred method of energy storage being electrolysis or the conversion of water to hydrogen and oxygen gases that are stored in towed pontoons which are recombined into water at night to generate electricity at night. In Wurst, et al. U.S. Pat. No. 5,518,205 altitude control, trim and pitch angle control is provided by a combination of the forward wing, rearward wing and propellers. As a result Wurst, et al. U.S. Pat. No. 5,518,205 does not have a cyclical thermal management system to compensate for the daily heating and expansion of the lifting gas and the nocturnal cooling and resulting decreased lift and contraction of the lifting gas. Wurst, et al. U.S. Pat. No. 5,518,205 utilizes the typical prior art altitude, pitch angle and trim control management by utilizing the forward wing, rearward wing and propellers.
Related high altitude long duration lighter-than-air platforms having a buoyancy control system for compensating for loss of lift due to nocturnal cooling is Schiff, et al. U.S. Pat. No. 3,174,705. The lifting gas density maintaining device in Schiff, et al. U.S. Pat. No. 3,174,705 is a microwave electromagnetic radiation absorbing device for absorbing beamed microwave electromagnetic radiation to raise the temperature of the lifting gas at night to compensate for the nightly cooling and resulting decreased lift and contraction of the lifting gas. Schiff, et al. U.S. Pat. No. 3,174,705 does not provide a mechanism for reducing lift during the daylight hours to maintain altitude and pitch attitude nor does Schiff, et al. U.S. Pat. No. 3,174,705 provide for reducing thermal stress on the skin or the replenishment of lifting gas lost by diffusion through the skin of the high altitude platform. Schiff, et al. U.S. Pat. No. 3,174,705 as a result does not provide a cyclical thermal management system to compensate for daytime heating with seasonal variation or the replenishment of lost lift resulting from the loss of lifting gas for long duration applications. Schiff, et al. U.S. Pat. No. 3,174,705 also does not chemically process either ballast or lifting gas to reduce skin stress and to compensate for diurnal heating and nocturnal cooling.
Nakada U.S. Pat. No. 5,348,254 pertains to a high altitude long duration lighter-than-air platform which utilizes solar power during the day but then burns hydrogen lifting gas at night and replaces the loss of lift by utilizing exhaust heat from the engine and recovering water at night. Like Schiff, et al. U.S. Pat. No. 3,174,705, Nakada U.S. Pat. No. 5,348,254 does not have a cyclical thermal management system for reducing skin stress during the day and maintaining a particular altitude during the day. Nakada U.S. Pat. No. 5,348,254 also does not have a recyclable cyclical thermal management system to cyclically manage the lifting properties of the lifting gas during both the daytime heating and the night time cooling cycles and for the replenishment of lifting gas lost through diffusion during the day or lifting gas that is burned during the night.
Kokai No. 54-35995 pertains to a high altitude balloon carrying water which at altitude is converted by electrolysis into hydrogen and oxygen using a solar cell. The hydrogen is used to increase lift as the oxygen is discarded. This prior art increases buoyancy but does not cyclically process ballast and lifting gas to reduce skin stress and to compensate for diurnal heating and nocturnal cooling to provide a cyclical thermal management system to compensate for both daytime heating, nighttime cooling and seasonal variations to provide for a long duration high altitude thermal management system.
Other high altitude long duration related art includes Stark U.S. Pat. No. 4,364,532 which circulates cool ambient air around solar cells for cooling to increase the efficiency of the solar cell; Eshoo U.S. Pat. No. 4,262,864 which has opaque and transparent skin surface sides which are alternatively oriented toward the sun for controlling ascent and descent; and Tockert U.S. Pat. No. 4,986,494 which recognizes the high altitude problem caused by diurnal heating and the necessity of protecting the envelope skin from rupturing by the venting of the lifting gas and the nocturnal cooling and decreasing lift and the necessity of dropping ballast to maintain altitude. Tockert U.S. Pat. No. 4,986,494 solves these problems by employing a variable volume balloon with a transparent envelope with a thermal trapping hood. Tockert U.S. Pat. No. 4,986,494 does not employ a semi rigid dirigible having a substantially constant outer surface shape and does not have a cyclical thermal management system for manipulating the temperature of the lifting gas, volume of the lifting gas or the weight of the ballast component. The related prior art does not provide a cyclical thermal management system for reducing skin stress and compensating for diurnal heating and nocturnal cooling or for controlling pitch attitude and providing for the replenishment of lifting gas lost in daily or seasonal cycles that is necessary for providing a long duration high altitude application.
The relevant prior art also includes a variety of passive skin systems for controlling altitude. In Pommereau U.S. Pat. No. 4,361,297 and Sanyo Electric Co. Ltd. Japan Appl. No. 4-26740 the upper part of the skin is transparent while in Graner French 2375-089 a metal foil is disposed between layers to reduce leakage. In CNES EP-31-981 the lower part of the balloon is transparent. None of these references alone or together provides for a combination of an active and passive system for maintaining a geostatic position.
Related prior art pertaining to manned balloons and dirigibles operating in the troposphere are believed only tangentially relevant due to the extremely different conditions in the stratosphere resulting in differences in processing hydrogen, oxygen and water as well as the utilization of active and passive systems to provide for long duration flights. The helium purification system of Haunschild U.S. Pat. No. 5,090,637 for manned dirigibles and the burning of hydrogen and recovery of water as a by-product of combustion in Fischer U.S. Pat. No. 2,078,532 and Russian 1,740,250 or the chemical conversion of natural lifting gases in Papst U.S. Pat. No. 3,897,032 are different than the invention as the prior art does not provide for a cyclical thermal management system for stratospheric applications to solve the problem of altitude variations resulting from diurnal heating and nocturnal cooling. Similarly dirigibles having multiple envelopes or layers of skin such as McCampbell U.S. Pat. No. 4,773,617 and the utilization of steam and water vapor to control lift and trim in Papst U.S. Pat. No. 3,456,903 are not particularly pertinent to high altitude applications in the stratosphere. The physical properties of water, steam and their mechanical migration through layers of envelope skin material is very different in the stratosphere than in the troposphere.